1. Field of the Invention
This invention pertains to the field of transporting goods as a load on a pallet, and, more particularly, to a slipsheet or divider sheet on which goods can be placed for transport.
2. Description of the Related Art
Goods, typically packaged in cartons or boxes, have for some time been placed on a pallet, which can be picked up by a fork-lift vehicle and moved on and off of a truck for transport from one place to another, about a warehouse for storage, and within a plant or factory where the goods are made or used. Wooden pallets are frequently used, which comprises a top platform for receiving and supporting the goods, a bottom platform that can rest on a floor or support surface, and rails or spacers separating the top and bottom platforms arranged in a manner so that the forks of a fork-lift vehicle can be received in the pallet. These wooden pallets are relatively expensive to purchase and require a great deal of room when transporting goods in a truck. Wooden pallets frequently require transport to a place where needed, and transporting empty wooden pallets is relatively expensive.
Cardboard and plastic slipsheets were developed as a space-saving device for supporting a load of goods. Slipsheets are much less expensive than wooden pallets and comprise a thin sheet of material that otherwise has the approximate dimensions of a typical wooden pallet. U.S. Pat. No. Re. 29,192, issued to Anderson et al., describes a slipsheet and a fork-lift and push-pull type truck, which is a fork-lift vehicle with an apparatus for handling a slipsheet, which Anderson et al. refer to as a slip pallet. Anderson et al. describe a slip pallet formed as a square or rectangular sheet of a synthetic resin of selected types of polyolefin. The sheet is proportioned to fit upon the forks or platen of a lift truck. The slipsheet has tabs at each edge, which can be gripped when the platen is thrust underneath the sheet, or the sheet can be pulled upon or pushed off from the platen by a push-pull apparatus used to modify a standard fork-lift vehicle. Anderson et al. describe their slip pallet as ordinarily carrying loads of boxes formed as interlocking layers, and an important feature of their slip pallet resides in providing a sheet having a greater coefficient of friction at the upper surface whereon the boxes are placed than at the undersurface, which is contacted by the platen.
The slip pallet of Anderson et al requires the upper surface of the slip pallet be textured or otherwise modified to increase the frictional resistance between the upper surface and the box load upon it. (Column 7, lines 39-42.) Anderson et al. found that the frictional resistance between the undersurface of the pallet and the platen could be minimized if the plastic sheet were roughened to a slight degree. (Column 8, lines 7-10.) Anderson et al. state that the textured surface of the plastic slip pallet can best be obtained when the web from which the pallets are formed is being manufactured. A standard manufacturing procedure for producing a web is by extruding hot thermoplastic material into the web form and finishing the web by moving it through sizing and cooling rollers. (Column 8, lines 13-19.) Anderson et al. suggest that their slip pallet can be made by roughening one of the finishing and cooling rollers about which the sheet moves, and a suitable method for roughening or texturing the finishing and cooling roller is by sandblasting the surface of the roller or by using other modes of roughening. (See column 8, lines 26-33.) Anderson et al. wanted to assure a comparatively high coefficient of friction between the surface of the plastic pallet and the paper material of an ordinary cardboard box and stated that a depth of approximately 60 micro-inches of surface roughness is satisfactory to achieve the high friction that they desired.